Our new Maximus to the Extreme (M2X) Sock is a heavyweight boot sock with all the great features of our Maximus Sock (Machine Wash and Dry, Ankle and Arch Support, Full Terry Loop Cushion matched with a reinforced nylon exoskeleton), but is 20% heavier for increased warmth & comfort. The M2X Alpaca Sock is also a boot length sock, fitting perfectly in between our crew height Maximus Sock and our over the calf height High Calf Boot sock.